The present invention relates to companding (compressing and then expanding), and more particularly to companding of video signals.
Recently there is interest in transmitting color video signals in time multiplexed analog component form (MAC) rather than the more conventional composite form. This transmission typically takes place by way of FM in a channel, which can be a video tape recorder (VTR) or a satellite transmission path. Such channels however contain noise, which degrades the quality of the reproduced picture. One way of improving the quality of the picture derived from such a noisy channel is by companding. In companding the amplitude of the video signal at the transmitter or recorder is compressed, thereby raising its average-to-peak ratio, and hence its realtive immunity to noise. At the receiver or playback apparatus the signal is amplitude expanded complementary to the compression function to restore its original amplitude distribution so as to obtain a correct signal for display. However since the luminance and chroma components have different amplitude distributions, a single companding law for either a composite signal or a MAC signal will not provide optimum noise reduction for both components.
It is therefore desirable to provide optimum companding for both luminance and chroma components of video signal.